This invention relates generally to digital image processing and more specifically to registration of two or more data sets.
Computer Axial Tomography (CAT), sometimes known generally as Computerized Tomography (CT), is used in many applications, especially medical radiology, to obtain two or three dimensional views of the interior of three dimensional bodies (CT or CAT Scans). The technique involves subjecting a three dimensional body to radiation that enters the body from many different angles. The amount of radiation that is scattered or reflected by the body is then detected as a function of the angle of scattering. The scattered data is then analyzed to construct an image of the interior of the body. A “slice” of the interior can be “reconstructed”, for example on a display screen, and viewed. The slice can be reconstructed for any desired angle of intersection with the body.
Image-based computer aided diagnosis (CAD) is a growing area of medical imaging. CAD is a diagnosis based on a comparison between two images (a first image and a second image) of anatomical structures of an individual. Each image is generated from separate data sets. As part of CAD, the data set associated with the first image is correlated with the data set associated with the second image so that a particular area of the first image is correlated with a particular area of the second image. As a result, a user of the CAD diagnosis can use a computer to select a section of the first image and the same section can appear on the second image. With a particular section of the images displayed simultaneously, a visual comparison and analysis can be performed.
The registration of two or more data sets of the same patient is typically important in computer aided diagnosis (CAD) and intervention. Registration of data sets is the correlation of a point in one data set to a point in the other data set.
For example, in the diagnosis of various cancers, one often wants to observe the tumor growth over a period of time. Multiple (e.g., two) scans of the tumor are typically taken to observe the tumor over a period of time. When multiple scans of a single patient are taken, several problems typically arise. First, it is often difficult to match the tumors in two different data sets (associated with two different scans) for a single patient. Second, registration can pose a problem. For example, there may be deformations and displacements due to body motion and body twists during one or more of the scans.
As a result, some type of elasticity is needed in the transformation between two data sets. For example, the transformation should address the motions and twists of the patient's body.